1986 Johnson 70-HP: 18 Questions

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
Whalertime
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1986 Johnson 70-HP: 18 Questions

Postby Whalertime » Wed Aug 21, 2019 11:32 pm

I have a 1986 Johnson 70 on my 1986 15-footer.

The 1986 Johnson 70 was great for my first four years of ownership. For the last year or more I have been battling constant stalling and a loss of power. I have seen 36-MPH. WOT before. Now maximum boat speed is at 23-MPH WOT and very slow acceleration onto plane from a standing start.


The carburetors have been taken apart multiple times. I have replaced fuel lines and spark plugs wires. Cylinder pressure readings are still good. The VRO is off, and I pre-mix oil and gasoline.

The 1986 Johnson 70 does run at low idle quite a bit. But I just can’t seem to help it reach its full potential and it’s been many a disappointing day on the water.

The other day the 1986 Johnson pulled a new one. It started at my usual meager 23-MPH, then started losing power slowly, until I just stoped. The problem seemed like an overheat because at low idle it would blow steam out the confidence stream outlet. I checked the water intake—no obstruction.

When I tilted the engine forward I noticed some gasoline drops on the water. I know there is an overflow. Maybe the engine is getting too much fuel to the high speed jets.

Then, if I increased engine speed, the confidence stream would start spitting out steady water. Low RPM produced steam, and high RPM produced water.

Then the engine stalled and I drifted for a while. If the engine were overheating, perhaps it needed a bit to cool off.

The other frustration is that the fuel hose primer bulb would not stay firm. Maybe that’s the problem right there.

I had my son pump the fuel hose primer bulb while I attempted several times to start the 1986 Johnson 70-HP engine.

All these problems started about a year ago, beginning with a loss of power.

Q1:What is loss of power most commonly caused by?

The carburetors have been rebuilt three times

The engine speed bogs when I push the throttle forward.

Then the engine takes forever to accelerate to get the boat on plane.

I’ve replaced the fuel pump and been through the electrical system.

Q2: Is the problem air?

Q3: If I were to re~power, what is the most powerful four-stroke-power-cycle engine recommended for an 1986 15-footer?

Q4: Why is the constant advice on these Johnson 70-HP engines with good compression to keep them?

“Just fix it, it’s a good motor.” Well I’m loosing faith, the thing has been in and out of the shop for over a year, no results.

Q5: Why was I getting steam?

Q6: Is steam terrible?

Steam seems pretty terrible. Once I got it started I had good water out the confidence stream outlet all the way back to the launch. But the engine still sounded rough.

Any advice or ideas are greatly appreciated.

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Re: 1986 Johnson 70-HP

Postby jimh » Thu Aug 22, 2019 9:14 am

A1: A gradual loss of engine speed at full throttle is usually indicative of a problem in fuel delivery.

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Re: 1986 Johnson 70-HP: Six Questions

Postby jimh » Thu Aug 22, 2019 9:16 am

A2: if you think air is being pulled into the fuel supply to the engine, temporarily insert a section of clear hose. Observe the fuel flow for bubbles.

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Re: 1986 Johnson 70-HP: Six Questions

Postby jimh » Thu Aug 22, 2019 9:21 am

A3: the maximum horsepower is listed on the capacity plate on the hull. The maximum power is not specified by two-stoke or four-stroke power-cycle engine designs.

A further consideration is engine weight. At the time the 15-foot hull was designed, most engines were two-stroke-power-cycle designs and relatively light. A modern four-stroke-power-cycle engine like a Yahama F70A would be about the highest power and lowest weight.

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Re: 1986 Johnson 70-HP: Six Questions

Postby jimh » Thu Aug 22, 2019 9:22 am

A4: the classic OMC three-cylinder 70-HP is perhaps one of the best outboard engines ever made and with proper maintenance could run forever.

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Re: 1986 Johnson 70-HP: Six Questions

Postby jimh » Thu Aug 22, 2019 9:24 am

A5: the presence of steam in the overboard indicator stream or confidence stream at idle speeds should be interpreted as lack of proper cooling water flow.

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Re: 1986 Johnson 70-HP: Six Questions

Postby jimh » Thu Aug 22, 2019 9:25 am

A6: the presence of steam in in the overboard indicator output in abnormal.

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Re: 1986 Johnson 70-HP: Six Questions

Postby jimh » Thu Aug 22, 2019 9:29 am

I advise you to have the engine serviced by an experienced mechanic who has many years of hands-on work with this 30-year-old engine.

Check the boat fuel system for obstructions.

Try running the engine on a different fuel tank, fuel hose, and primer bulb assembly.

Do not run the engine if the cooling water flow is insufficient at low RPM. Have the water pump serviced.

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Re: 1986 Johnson 70-HP: Six Questions

Postby biggiefl » Thu Aug 22, 2019 10:42 am

Sounds like you need a new mechanic.

Steam is bad--very bad.

What are your compression numbers?

That boat properly setup should run 45-MPH or faster. The three-cylinder OMC engines are the strongest 70-HP I have ever driven, but I have blown one up.

Struggling to plane and low idle says that engine is probably running on two cylinders.

Does your overheat alarm work?

If not it should.

My engine choice would be a Suzuki DF70. I am not impressed with the F70 performance so far.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

Whalertime
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Re: 1986 Johnson 70-HP

Postby Whalertime » Thu Aug 22, 2019 12:21 pm

jimh wrote:A1: A gradual loss of engine speed at full throttle is usually indicative of a problem in fuel delivery.

Thanks I will check the fuel pump, I replaced it once but perhaps it’s time again. I really appreciate everyone’s input. Thanks.

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Re: 1986 Johnson 70-HP: Six Questions

Postby Whalertime » Thu Aug 22, 2019 12:21 pm

jimh wrote:A2: if you think air is being pulled into the fuel supply to the engine, temporarily insert a section of clear hose. Observe the fuel flow for bubbles.


That’s a great idea thanks.

Whalertime
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Re: 1986 Johnson 70-HP: Six Questions

Postby Whalertime » Thu Aug 22, 2019 12:29 pm

jimh wrote:A3: the maximum horsepower is listed on the capacity plate on the hull. The maximum power is not specified by two-stoke or four-stroke power-cycle engine designs.

A further consideration is engine weight. At the time the 15-foot hull was designed, most engines were two-stroke-power-cycle designs and relatively light. A modern four-stroke-power-cycle engine like a Yahama F70A would be about the highest power and lowest weight.

Thanks I’ll look into weight specs and do some research. The reason I think a 4 stroak may be better is because I do so much slow canal cruising and I know the two strokes like to run wide open.

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Re: 1986 Johnson 70-HP: Six Questions

Postby Whalertime » Thu Aug 22, 2019 12:41 pm

jimh wrote:A4: the classic OMC three-cylinder 70-HP is perhaps one of the best outboard engines ever made and with proper maintenance could run forever.


I completely agree and this is my dilemma. I believe it’s the best motor for the boat which is why I’ve been dumping money into it, I’m just not seeing any results. Still stalling, not accelerating to full engine speed, and now overheating.

Since I bought the boat I have had the engine regularly service once or twice a year, and as problems arose. I’m just not sure when to give up putting money into the engine. The mechanic I found is in his 70’s and knows Johnson engines, but he has gotten nowhere with it.

Whalertime
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Re: 1986 Johnson 70-HP: Six Questions

Postby Whalertime » Thu Aug 22, 2019 12:42 pm

jimh wrote:A5: the presence of steam in the overboard indicator stream or confidence stream at idle speeds should be interpreted as lack of proper cooling water flow.


I’ll run some salt away through it, and it is possible that I picked something up.

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Re: 1986 Johnson 70-HP: Six Questions

Postby Whalertime » Thu Aug 22, 2019 12:46 pm

jimh wrote:I advise you to have the engine serviced by an experienced mechanic who has many years of hands-on work with this 30-year-old engine.

Check the boat fuel system for obstructions.

Try running the engine on a different fuel tank, fuel hose, and primer bulb assembly.

Do not run the engine if the cooling water flow is insufficient at low RPM. Have the water pump serviced.



Cool, I have changed out tanks, not lines though, with the same concern. I know the water high temp shut off works because we checked that, but there is no audible buzzer.

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Re: 1986 Johnson 70-HP: Six Questions

Postby Whalertime » Thu Aug 22, 2019 12:50 pm

biggiefl wrote:Sounds like you need a new mechanic.

Steam is bad....very bad. What are your compression numbers? That boat properly setup should run 45+. The 3cyl OMCs are the strongest 70hp I have ever driven but I have blown one up. Struggling to plane and low idle says she is probably running on 2cyls. Does your overheat alarm work? If not it should. My choice would be a 70hp Suzuki as I am not impressed with the F70 performance so far.



I agree that a new mechanic may be a valid suggestion. 125 Across all three cylinders. It does feel like I’m running on two cycles, what causes that? No alarm but I think the shut off works as I had that tested.
I’ll check the Suzuki.

Q7: is the Suzuki a two stroke?

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Re: 1986 Johnson 70-HP: Six Questions

Postby biggiefl » Thu Aug 22, 2019 2:21 pm

Nobody makes two-strokes anymore except E-TEC and OptiMax. Not sure if Yamaha is still doing their HDPI.

You would know if running on two cylinders and easy to check.

If fuel pump was bad you would eliminate that by pumping the bulb which will fill the bowls.

I would try a new fuel line and bulb and see if that works or pumping it while driving does.

If not than it could be electrical or even something more obscure like a bad reed block.

Overheating can be waterpump, salt scale, thermostats, poppet valves.

How clean are the plugs?

They should be dirty or brownish. If really clean then you might have water ingestion. That usually only occurs on one cylider and with these its usually the middle one.

How hot is it getting? You should be able to put your hand on the block for a second or two. If it is hotter than that you have a problem.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

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Re: 1986 Johnson 70-HP: Six Questions

Postby L78steve » Fri Aug 23, 2019 1:13 pm

Whalertime wrote:I have changed out tanks, not lines...


Why did you not change out the fuel lines? Its very possible the inner fuel hose liner is collapsed and restricting flow.
1988 15' Sport, 89 Johnson 70HP
1998 22' Progression Merc 300XP
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dg22
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Re: 1986 Johnson 70-HP: Six Questions

Postby dg22 » Fri Aug 23, 2019 3:48 pm

fuel hose primer bulb would not stay firm


It almost sounds like the tank is not getting air so the fuel pump is sucking in the primer bulb on the fuel hose which could be caused by the air vent on tank being shut or clogged.

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Re: 1986 Johnson 70-HP: Six Questions

Postby Whalertime » Sun Aug 25, 2019 11:30 am

Well I had a little time to investigate yesterday.

Sorry I said I had not replaced the fuel lines. What I meant was not recently not since the loss of power concern. About two years ago I replaced all fuel lines including the little tiny lines before the carburetors. I also put a new fuel tank associated bulb, lines, RACOR fuel-water separator filter, as well as a new fuel pump.

My mechanic claimed we were pumping good fuel at the pump. So I don’t think the lining on those fuel lines is going just yet.

I am seeing fuel puddling a little after the fuel pump just before the carburtors right at that little elbow, this could be part of the problem.

Q8: where do you buy those crappy little elbows and associated fuel parts?

Also I have a less than satisfactory fuel connection point on both tank and motor--okay I’ll deal with that ASAP I’m sorry okay can’t find the motor side fuel inlet. This will help keep the system properly pressurized.

Q9: are there any of the VRO-style fuel inlets for the motor left on this planet?

But I really don’t think this it is related to my massive loss of power. [Boat speed] Used to [be] 35 to 36-MPH, and now I’m lucky to get much over 23-MPH.

I start the motor and it blows tons of smoke.

Q10: is it normal for an old two-stroke to blow tons of smoke after it starts?

No VRO mixed oil 50-1. [The engine accelerates to] 5000-RPM wide open out of the water. In the water 2,000 to 3000-RPM.

Shut off the engine and pop the plugs, remember I’m getting concerned about overheat. On the middle cylinder spark plug around the top of the threads there is rusty particulate, This I will watch.

I clean all the plugs and wire ends and put back together. The plugs were dirty.

I put an email out to Blackbird Motors to see about re-build costs. I know some folks on this forum have regarded them as a good business.

Q11: is [Blackbird Motors] an only service just re-boring the cylinders or do they do complete overhauls?

In a few days I will take the Johnson 70 to my mechanic.

First, I will try to repair any fuel stuff I have seen.

Q12: why the stalling and great loss of power?

We have had those carburetors rebuilt three times this year.

The mechanic checked out the electrical last session and said it was good. Compression was good.

Q13: What should I have him look for?

Q14 : where can I get a motor side fuel inlet ?

Q15: are steam and slight rust on middle cylinder spark plug [an indication that] the cylinder wall [is] corrupted?

Q16: Where can I buy the parts for tightening up the tiny ID lines after pump?

Q17: Is Blackbird a full re-build including electrical?

Q18: What should I have my Johnson mechanic tackle to get rid of the loss of power?

I feel certain [the cause is] not fuel. Pumping [the primer bulb underway] only bogged down the engine. Pushing the primmer switch almost made the engine stall while under[way].

Thanks for all the advice. It is appreciated.

While I do re-fits and maintain bigger boats, keeping up with many types of systems, I am somehow am not so confident with outboard engines, even as simple as this one.

So thanks everyone for the responses I hope I can get her up and running again.

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Re: 1986 Johnson 70-HP: Six Questions

Postby biggiefl » Mon Aug 26, 2019 9:39 am

Run it again and let your mechanic decipher the plugs. Sounds like water in middle cylinder. Probably time to re-power if the case.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

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Re: 1986 Johnson 70-HP: Six Questions

Postby L78steve » Mon Aug 26, 2019 12:38 pm

If [the engine is] getting some water in the cylinders, [the cause] could be a faulty exhaust cover gasket-- an easy fix.

You should not rev the engine without a load. If you must, use a test prop, a special part not a regular prop.

Water in the cylinders could be your problem. It is very common for the exhaust cover gaskets to blow out.
1988 15' Sport, 89 Johnson 70HP
1998 22' Progression Merc 300XP
1961 12' Allstar FG 73 Evinrude 25

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Re: 1986 Johnson 70-HP: Six Questions

Postby L78steve » Mon Aug 26, 2019 12:49 pm

The fuel line connector is not [the cause of the problem with the engine].

You don't need the obsolete VRO style if [the gasoline and oil are pre-mixed].

The parts for securing the fuel lines are [cable] ties. Use the type that have the stainless tab not the toothed style.

The plastic elbows can be purchased at a dealer or [on-line].
1988 15' Sport, 89 Johnson 70HP
1998 22' Progression Merc 300XP
1961 12' Allstar FG 73 Evinrude 25

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Re: 1986 Johnson 70-HP: Six Questions

Postby biggiefl » Mon Aug 26, 2019 1:30 pm

I would have assumed that your "mechanic" has already checked [the 1986 Johnson 70-HP engine] water jacket gasket as mentioned above.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

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Re: 1986 Johnson 70-HP: Q10

Postby jimh » Tue Aug 27, 2019 7:37 am

Whalertime wrote:Q10: is it normal for an old two-stroke to blow tons of smoke after it starts?


A two-stroke-power-cycle engine should not have excessive smoke in the exhaust immediately after start-up, unless there is some cause for there to be too much oil in the fuel. Having too much oil in the fuel could be due to the engine not being in proper tune and not being properly started, causing an accumulation of unburned fuel in the cylinders, which, once the engine starts, then gets burned off and creates smoke.

The notion that any two-stroke engine must be difficult to start, will smoke like a campfire, and will run poorly is unfounded. A two-stroke engine in proper tune, being started with the recommended starting procedure, and having a proper fuel mixture should start easily, run smoothly, and produce little smoke.

Smoke in the exhaust is also related to the quality of the two-cycle oil being used. If using a modern, semi-synthetic two-cycle oil, there is will be very little smoke in the engine exhaust.

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Re: 1986 Johnson 70-HP: Q17

Postby jimh » Tue Aug 27, 2019 7:38 am

Whalertime wrote:Q17: Is Blackbird a full re-build including electrical?


Rather than solicit advice about what services the firm "Blackbird" can offer to you, you should contact them directly and discuss this with them. The firm itself can give you an authoritative answer to your question.

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Re: 1986 Johnson 70-HP: Q15

Postby jimh » Tue Aug 27, 2019 7:40 am

Whalertime wrote:Q15: are steam and slight rust on middle cylinder spark plug [an indication that] the cylinder wall [is] corrupted?


The integrity of the cylinder wall can best be determined by inspection with a borescope.

I don't think the engine would be able to run at all if the middle cylinder wall had a hole in it.

A more reasonable interpretation of the presence of rust and water on a spark plug is a gasket has failed, allowing cooling water to enter the cylinder.

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Re: 1986 Johnson 70-HP: Q12

Postby jimh » Tue Aug 27, 2019 7:50 am

Whalertime wrote:Q12: why the...loss of power?


In a three-cylinder engine, a loss of power may be due to one cylinder not firing.

A good preliminary step in diagnosis of problems with power loss is to verify that all cylinders are receiving spark voltage and are firing.

A good way to verify spark voltage and spark plug firing is to use an in-line spark gap tester.

To use an in-line spark gap tester, the spark gap tester is inserted into the spark plug wire at the spark plug. The engine is started with the cowling still removed. Visually observe the spark gap in the in-line spark gap tester, looking for a steady arc across the gap corresponding to the periodicity of that cylinder firing.

If the spark voltage is strong it will fire across the gap in the in-line tester and the gap in the plug.

An in-line spark gap tester that I have used to perform diagnostic testing on individual cylinder spark firing with excellent results is an 20610 LISLE In-line Ignition Spark Tester, pictured below.

Image
In-line spark gap tester made by LISLE and widely available.

To anticipate a possible additional question about where to purchase a LISLE model 20610 In-line Ignition Spark Tester, I bought mine at my local Evinrude dealer. LISLE products are often sold at automotive parts stores.

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Re: 1986 Johnson 70-HP: 18 Questions

Postby jimh » Tue Aug 27, 2019 7:52 am

A good source of general advice on how to being evaluation of an outboard engine is given in a REFERENCE article that discusses a method for assessing (used) outboard engines. Please read

Assessing Used Outboard Engines
http://continuouswave.com/whaler/reference/outboardCheck.html

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Re: 1986 Johnson 70-HP: Q13

Postby jimh » Tue Aug 27, 2019 8:14 am

Whalertime wrote:The mechanic checked out the electrical last session and said it was good. Compression was good.

Q13: What should I have him look for?


Rather that try to direct the mechanic to look into a particular cause of the problems with this engine, you should give the mechanic a carefully written and concise summary of the nature of the problems, when the onset of the problem occurred, and any changes you have made to the boat, the fuel system, the carburetors, the engine wiring, the engine fuel hoses, and so on.

Trying to direct the mechanic to a particular component for him to test really removes from the diagnostic procedure the mechanic's own experience and skill. Rather than substituting your estimate of where the source of the problem is located, let the mechanic use his skill and experience to direct his work. In addition to simply paying the mechanic for his labor, you should consider that you are also hiring him for his expertise and experience with this engine and its typical problems.

As mentioned already, if a particular mechanic has already been hired and paid for several work sessions and has failed to find the actual cause and failed to provide a remedy, the time to hire a different mechanic may be at hand.

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Re: 1986 Johnson 70-HP: 18 Questions

Postby Don SSDD » Fri Aug 30, 2019 3:45 pm

Do these three-cylinder outboards have three-carburetors?

If yes, drain the float bowl in each carburetor, and see what comes out.

I’m learning this stuff.

If you loosen the float bowl screw, when you pump the primer bulb you should get fuel leaking out of the screw.

Do this even if there is only one carburetor to see if clean gas emerges from the bowl or if there is contamination.

I have worked only on V4 engines.
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Former Owner 1991 Guardian 19 with 1994 Evinrude V4 140HP
Former owner 1987 Montauk with 1998 Mercury 90HP
Nova Scotia

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Re: 1986 Johnson 70-HP: 18 Questions

Postby jimh » Sat Aug 31, 2019 12:44 pm

Don SSDD wrote:Do these three-cylinder outboards have three-carburetors?


Usually a two-stroke-power-cycle classic outboard engine with carburetors will have individual carburetors for each cylinder.

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Re: 1986 Johnson 70-HP: 18 Questions

Postby Whalertime » Fri Sep 27, 2019 12:13 am

I wanted to thank everyone for their thoughts and time on the subject of my Johnson 70. Last week I brought the motor in and we removed and replaced the head gasket. Because of the rust particulate on the spark plug we went through the process of pulling the head. The bolts needed heat and a good deal of encouragement to remove. There was a lot of corrosion in the water ways, and the head gasket was in bad shape. It was noted that the top carb was also flooding and not running. This was removed and cleaned.

I decided to replace all the little fuel lines on the engine and inspect the fuel system in the process. I started with the lines from the tank, replaced the fuel bulb with an OEM bulb, replaced the racor filter, fuel inlet connection on the engine, I noticed that the fuel filter on the engine had a crack and also replaced. When the system was pressurized I found that fuel was leaking out of the hose connection to the bottom carburetor. I checked the fuel pump and it is clean and in good shape and I tested the primer pump solenoid. I replaced the elbow and all the little tees and the small fuel lines that go to the carbs. When I pump the bulb now it primes with in three to four pumps. I bought a quality synthetic two stroke oil and mixed it with a fresh tank of gasoline 50:1. The mechanic adjusted the linkage and worked with the idle as I was stalling between gears on initial sea trial.

On the second sea trial after the above work was completed. I launched the boat which started after a few tries with some smoke. It ran well at low speed with no stalling between gears as I have grown fearfully accustom to, and it sounded nice at high RPM as well.

With wind and tide I exceeded 30-MPH trimmed up and turned the boat around and saw 31-MPH. Now I know this might not be a big whoopdedo to some, as I have heard reports of 42-MPH with a Johnson 70 on a SSL 15, but top speed is 36 on this boat (gps speed over ground). So I feel like we are getting somewhere. But knock on wood, I am hoping I can achieve the same faith and trust I once had in this old motor.

This week I had the Stainless Steel prop reconditioned and stuck it back on the boat this morning, unfortunately I got home to late from work to launch and test it.

I did get a good deal of information from Blackbird Motors. Nice guys. They were prepared to re-build the block. I went to the old owner of my boat (a friend) who has some trailer registration documents I needed, he informed me that the block was rebuilt in 2011. The middle cylinder was re-sleeved. So I determined not to repeat the process as the cylinder walls looked good and the compression is good.

Again thanks for all of your helpful comments. I am looking forward to a cruise this weekend.

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Re: 1986 Johnson 70-HP: 18 Questions

Postby jimh » Fri Sep 27, 2019 8:29 am

Your follow up to this lengthy discussion is good to have. I think you have rescued that classic OMC three-cylinder engine from a undeserved oblivion.

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Re: 1986 Johnson 70-HP: 18 Questions

Postby biggiefl » Fri Sep 27, 2019 10:18 am

How far out did you have it trimmed to get 36mph? If not trimmed to the max, that is about what you will get. Did you ask the owner what it used to run when he had it?
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

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Re: 1986 Johnson 70-HP: 18 Questions

Postby Whalertime » Sun Sep 29, 2019 10:54 pm

biggiefl wrote:How far out did you have it trimmed to get 36mph? If not trimmed to the max, that is about what you will get. Did you ask the owner what it used to run when he had it?


I was not using the trim at all. When I went 36 mph it was just after I bought the boat (5 years ago) the engine just had a lot more power. I’m still not seeing that degree of speed or jump coming out of the hole with my Johnson 70. But if it runs smooth and it’s reliable I can deal with a little less power. I do mostly back canal puttering in the boat anyhow. I think I did speak to the old owner a while back, he told me someone made adjustments to the engine to get a little more Power out of it. I’ll have to re-check with him on what was done. Now with max trim I am getting 31.

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Re: 1986 Johnson 70-HP: 18 Questions

Postby Whalertime » Sun Sep 29, 2019 11:19 pm

jimh wrote:Your follow up to this lengthy discussion is good to have. I think you have rescued that classic OMC three-cylinder engine from a undeserved oblivion.


Yes I think we did, your responses have been very valuable.

Had a nice tube session with my son and daughter on Sat. My daughter did not want to go and when I asked her why she said “because I don’t want the boat to stall.” After some convincing she came along and had a blast driving.
I spent the rest of the weekend cleaning then polishing the boat.

Thanks you so much for your time and answers to my long winded questions.

biggiefl
Posts: 256
Joined: Thu Jul 11, 2019 1:31 pm
Location: south Tampa Bay area
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Re: 1986 Johnson 70-HP: 18 Questions

Postby biggiefl » Mon Sep 30, 2019 2:30 pm

Start saving for a new engine. You would get 31 with a 35 or 40hp. Trimmed out should be at least 40, more like 45+ setup correctly and no gear.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

Whalertime
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Joined: Sun Dec 02, 2018 6:01 pm

Re: 1986 Johnson 70-HP: Six Questions

Postby Whalertime » Mon Sep 30, 2019 10:08 pm

L78: What is the boat speed [of your SPORT 15] with the Johnson 70 at WOT?

L78steve
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Joined: Thu Aug 22, 2019 9:51 pm
Location: Hendersonville NC

Re: 1986 Johnson 70-HP: Six Questions

Postby L78steve » Tue Oct 01, 2019 4:04 pm

The boat speed is 40-MPH with 13x17 OMC aluminum propeller and the engine mounted all the way down and trimmed as far as it will go before blow out.


I've been battling the hot alarm demons. Finally did the updates and got that straightened out.
1988 15' Sport, 89 Johnson 70HP
1998 22' Progression Merc 300XP
1961 12' Allstar FG 73 Evinrude 25

biggiefl
Posts: 256
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Location: south Tampa Bay area
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Re: 1986 Johnson 70-HP: 18 Questions

Postby biggiefl » Mon Oct 07, 2019 10:53 am

Steve you should be running a 13x19 SST on that and raise that puppy up. Max rpm on the 89 is 6k.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

L78steve
Posts: 11
Joined: Thu Aug 22, 2019 9:51 pm
Location: Hendersonville NC

Re: 1986 Johnson 70-HP: 18 Questions

Postby L78steve » Mon Oct 07, 2019 2:05 pm

biggiefl wrote:Steve you should be running a 13x19 SST on that and raise that puppy up. Max rpm on the 89 is 6k.



Are you sure it will spin the 19? Currently running at 5400RPM. In order to raise it up I will have to go with a jack plate. Not sure I want to go that route with it, Its a nice clean original that was put up in a barn back in 94.
1988 15' Sport, 89 Johnson 70HP
1998 22' Progression Merc 300XP
1961 12' Allstar FG 73 Evinrude 25

biggiefl
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Joined: Thu Jul 11, 2019 1:31 pm
Location: south Tampa Bay area
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Re: 1986 Johnson 70-HP: 18 Questions

Postby biggiefl » Tue Oct 08, 2019 11:14 am

Your tach may not be accurate. I have owned 3 with 86-91 70's and I ran 2 with 13x19 SST and getting more than 5400rpm. I had bolted all the way up that I ran a 13x20 and it would just sit at 6k at 48+mph.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

L78steve
Posts: 11
Joined: Thu Aug 22, 2019 9:51 pm
Location: Hendersonville NC

Re: 1986 Johnson 70-HP: 18 Questions

Postby L78steve » Thu Oct 10, 2019 7:19 pm

I'll check it this weekend with a tach hooked up to the crank. My ear says the boat tachometer is correct. It is an old-stock OMC tachometer.
1988 15' Sport, 89 Johnson 70HP
1998 22' Progression Merc 300XP
1961 12' Allstar FG 73 Evinrude 25

biggiefl
Posts: 256
Joined: Thu Jul 11, 2019 1:31 pm
Location: south Tampa Bay area
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Re: 1986 Johnson 70-HP: 18 Questions

Postby biggiefl » Fri Oct 11, 2019 10:09 am

Many outboard engine tachometers are adjustable, so check the pole switch position.

I even ran a 19 SST on my 60-HP The 48spl ran a 17 aluminum. I have owned five or six 15's.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

L78steve
Posts: 11
Joined: Thu Aug 22, 2019 9:51 pm
Location: Hendersonville NC

Re: 1986 Johnson 70-HP: 18 Questions

Postby L78steve » Sun Oct 13, 2019 5:19 pm

The engine tachometer is spot on at 800 and 2,000-RPM. I compared it to a SW hand tach.

The boat speed is 40-MPH with just me. Boat speed is 38-MPH with me, wife, and two dogs.
1988 15' Sport, 89 Johnson 70HP
1998 22' Progression Merc 300XP
1961 12' Allstar FG 73 Evinrude 25